I used to fool with springs a lot. I found it necessary to calibrate them. I made a rig so I could measure the deflection and the load and also the width when loaded. This gave me the spring rate and the height when installed. I made it all from stuff on hand. The main T weldment was 4" channel welded back to back to form square sections. It was a long bottom section and an offset upright post in the middle. It had a stick out cap on the upright to push against and tabs on the bottom part to mount various length attachments for the shackles. The load was by my old port a power and the loads was measured by a home made load cell. The load cell is made from an 1 1/8 dia. wheel cylinder. A pressure gauge was screwed in the tubing boss. I calibrated mostly the 28-34 front springs but I did make another rig to test the longer springs. Friends would bring springs and we would test them for rate and capacity. Leaves were pulled or added as required. It was fun. As an aside. You want the spring to flex to about 3-4 in under static load. Auto engineers talk about deflection more than rate. The spring rate wanted depends on the load. Say you have a car and the supported load is 800 lbs. The spring rate is 125 per side so 250 total. The deflection would be 800 divided by 125 so 3.1 in. Load in lbs divided by lbs per inch rate gives deflection in inches. Any body finds this maybe interesting, let me know and I will drag some of the old stuff out for pics.
I found the stuff so I can show something. The spring shackles are not in tension because I needed the port-a-power to spread the spring. The spring hangers are too long. The port-a-power just sits on the top of the gauge and the end goes in the cup at the top. It is missing the scale to measure the deflection. I would put wood blocks under the spring ends and apply pressure to spread the springs and hook up the shackles I would measure a starting dimension then increase the pressure in 100 lb increments and measure the height. At first I would graft the results but quickly just used widely separated points and figured it out. It is crude as hell but worked just fine. The load sell has been very useful. I use it to weigh lots of stuff. I have weighed the ends of cars by putting it on a floor jack. I drilled holes in the corners so I can use it for weighing stuff that is hanging like from the engine hoist. The spring is one of my fiberglass ones I made long ago.
That black thing on top of the spring measures the load on the spring. It is a 1 1/8” dia wheel cylinder so it has a cross section area of 1”. It reads the load in pounds directly on the pressures gauge screwed into the side. The thing is just the wheel cylinder brazed to the bottom plate and a plunger with an O-ring welded to the top plate.
Hey,Andy; Care to do a how-to-Tech on DIY 'glass spring(s) ? . TIA. . Also, did you use an o-ring or a oem-style cup to seal the plunger to the wheel cyl? I like the concept. Marcus...
I thought about using a cup. I wanted a lot of bar down in the cylinder. The cup would have been below the bleed screw. I cut a groove in the bar and used the O-ring. Ps, The top will not fall out. You would have to pull 14 lbs to get it out. Air pressure holds it in.
When I measured the rate on my '37 truck leaf springs, I made an axle for one end that went through the bushing. On each end was a roller bearing so it could roll with no resistance. I set each end on steel plates for a smooth surface then set a digital scale at the peak of the arc. All this was under the trailer hitch of my Toyota truck held up by a floor jack. To measure the rate, I simply lowered the truck on to the spring watching a ruler, when it lowered 1 inch, I read the scale, then went one more inch and read the scale. It was linear measurement, no matter how many inches I went, I got scared and quit before three inches. It was accurate was enough to verify what I had and not that hard to do. I did have a couple small chains around the spring hooked under the truck, just incase! Mine were way heavier then needed. The small load meter thing would have be pretty handy to have.
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